22 lines
773 B
Haskell
22 lines
773 B
Haskell
isSortedGradually' :: (Integer -> Integer -> Bool) -> Bool -> [Integer] -> Bool
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isSortedGradually' f mercy (x1:x2:xs) =
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(diff >= 1 && diff <= 3 && f x1 x2 && isSortedGradually' f mercy (x2:xs))
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|| mercy && isSortedGradually' f False (x1:xs)
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where diff = abs (x1 - x2)
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isSortedGradually' f mercy _ = True
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isSortedGradually f (x:xs) = isSortedGradually' f True (x:xs)
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|| isSortedGradually' f False xs
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isAscending :: [Integer] -> Bool
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isAscending xs = isSortedGradually (<) xs
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isDescending :: [Integer] -> Bool
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isDescending xs = isSortedGradually (>) xs
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isSafe :: [Integer] -> Bool
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isSafe xs = isAscending xs || isDescending xs
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main :: IO()
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main = interact $ show . sum . map (fromEnum . isSafe . map read . words) . lines
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